A precast concrete wall structure and method for forming a wall structure are disclosed. A forming member is positioned within a casting bed. The forming member comprises a layer of insulating material defining a plurality of integrally-formed rectangular protrusions extending in a parallel and spaced-apart relationship to one another to define a plurality of rectangular-shaped channels therebetween. The forming member also defines at least one cutout for defining a first portion of a fastener for securing the wall structure to a support structure. A second portion of the fastening member is positioned within the cutout. Uncured concrete is placed within the casting bed and allowed to cure.